The steroids in general form an important group of the modern drugs. An important one of these, .beta.-sitosterol, is both a lipotropic agent and a starting material in the production of steroids.
The technical grade .beta.-sitosterol obtained according to this invention is pure enough for the use as starting material for steroids and is also in a form which is easily purifiable by conventional methods to pharmaceutical grade .beta.-sitosterol.
Many processes for the separation of sterols from various sources are known but there are not many processes which concern particularly the separation of .beta.-sitosterol from the neutral fraction obtained in the sulfate process of pine wood and hardwood. The U.S. Pat. No. 2,835,682 for example concerns the recovery of sterols from sterol-containing materials in general. According to this patent a sterol containing mixture is fractioned in a normally gaseous hydrocarbon, e.g. propane, to give a sterol-enriched fraction, which is saponified in alcholic alkali solution whereafter the sterols are crystallized by adding water and cooling. U.S. Pat. No. 2,866,797 is concerned with the crystallization of sterols from unsaponifiables obtained from vegetable oils, tall oils, sugar cane oil and the like. The unsaponifiable fraction is extracted with ethylene dichloride, and small amounts of water and methanol are added to precipitate the sterols.
Of newer publications can be mentioned U.S. Pat. No. 3,961,211, which concerns a process for preparing sterols from plant sources, especially tall oil pitch, by extraction in a water-alcohol-hydrocarbon mixture followed by saponification and subsequent recrystallization and leaching. The process, which is not comparable to the process of the invention as the starting material is different, gives a good yield of a mixture containing .beta.-sitosterol and campesterol.
In Chemical Abstracts, Vol. 81 (1974) 51409 v a method is described for purifying crude phytosterol derived from sulfate soap to .beta.-sitosterol. The process comprises dissolving in ligroin at 70.degree.-75.degree. C., extracting with 40 percent ethanolic solution at 65.degree.-70.degree. C., and washing with water at 65.degree.-70.degree. C. The solution is then cooled to give 90.4 percent pure .beta.-sitosterol, the yield being 69.5 percent.
U.S. Pat. No. 4,044,031 disclosed a process for the separation of sterols from e.g. the same neutral fraction as in the present invention. The process of U.S. Pat. No. 4,044,031 consists of dissolving the neutral fraction in a water-immiscible solvent, extracting the solution with a hydrophilic phase containing small amounts of water, and recovering sterols from the hydrophilic phase. This process, which utilizes extraction with two solvent phases, can be carried out continuously utilizing a counter-current extraction process.
As compared with all above mentioned processes the process of the present invention is inexpensive and simple and gives a product of high quality. The betulin, which usually accompanies the .beta.-sitosterol in the purification processes and which is a toxic agent, is completely removed in the process of the present invention.